Simple Strategies for Keeping Cool

Some easy, low-tech strategies can help keep you relatively comfortable in hot weather

Posted on Jul 6 2010 by Alex Wilson

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While blocking sunlight on the outside of a house is better than using interior insulating blinds to reflect sunlight back out through windows, the latter can still make a big difference.

We’re into those hot days of summer--really hot--with temperatures predicted in the mid- to upper-90s, even in Vermont, this week. In this column I’ll provide some simple tips for keeping (reasonably) cool in hot weather or, if you use air conditioning, operating that air conditioning equipment most efficiently.

Keep the sun out

Shading windows is the easiest way to keep your house cool or keep your air conditioning bills down. Pulling down interior window blinds will help (the more reflective the outer surface of the blinds the better), but shading is even more effective if you can block the sunlight on the outside of your windows. In Europe, exterior roller blinds are often used, and these are beginning to catch on here, but they’re not yet widely available. I’ve improvised exterior shading on a wide patio door facing west by propping up a tarp on the outside of the door, and that makes a huge difference. Climbing vines on a trellis, nearby trees, large potted plants that can be rolled in front of doors or windows, and awnings can also help a lot. If there’s no way to block that sunlight on the outside of windows and patio doors, install and use interior blinds.

Keep hot air out

Closing windows on hot days seems counterintuitive to some (don’t we want open windows for breezes?), but it makes sense. I have a digital indoor-outdoor thermometer on the north side of our house, and I use that to gauge when to open and close windows. When it’s hotter outside than inside, I close the windows, and when it’s cooler outside than inside, I open them. That’s pretty simple--but it does require paying attention and opening and closing windows fairly often. In hot weather, I often open up the house at night and close it up during the day.

Minimize interior heat loads

Try to avoid generating a lot of heat and humidity in your house in hot weather. Consider meals that don’t require much cooking. Turn off lights when not needed (and replace incandescent light bulbs with CFLs). Make sure televisions and stereo systems are turned of when not in use (putting them on power strips allows you to turn them totally off to eliminate the “phantom loads”). Only run your dishwasher when totally full, and operate it in the middle of the night if possible. Wash clothes in cold water and hang outside to dry rather than using the dryer.

Use a fan to circulate air when you’re in a room

All other things being equal, a breeze will keep you a lot cooler. If you’re normally comfortable at, say, 72 degrees, using a ceiling fan or oscillating desk fan may enable you to be just about as comfortable with an air temperature of 75 to 80 degrees--because the moving air evaporates moisture from your skin. Note that fans don’t actually cool the air (in fact, they increase air temperature slightly from the motor’s waste heat), so turn them off when you leave the room.

Wear lighter clothing

This is common sense, but bears repeating. Shorts, and loose-fitting shirts, blouses, and dresses allow more air circulation next to your skin and will keep you cooler. At the office, convince your manager to relax the dress code during hot weather.

Control your air conditioner wisely

To save energy, raise the temperature setting on your air conditioner’s thermostat when you’re not home. Keep windows closed when using an air conditioner--not only to keep hot air out, but also to keep down indoor humidity.

These strategies can help you save money and maintain greater comfort during hot weather. They can also be lifesaving for vulnerable people (the elderly or ill) in the event of a power outage--as can happen in very hot weather when electricity demand is the highest. In late June, rolling brownouts affected over 100,000 customers in Brooklyn, New York; a more extended blackout could be deadly if it were to occur during very hot weather. If you lose power and don’t have air conditioning, simple passive measures will be critically important.

In addition to this Energy Solutions blog, Alex writes the weekly blog on BuildingGreen.com: “Alex’s Cool Product of the Week,” which profiles an interesting new green building product each week. You can sign up to receive notices of these blogs by e-mail—on the BuildingGreen.com blog page enter your e-mail address in the upper right corner.

Our air conditioner just went out at the office, so these will come in handy. Have been doing some experimenting on my own trying to learn how to stay cool without AC here in NC which is very difficult. Probably a little different climate up there in VT but we typically have hot and humid summers here. I recently purchased some $12 thermometers to track the temp and humidity inside and outside my home trying to figure out if or when I can open the windows to allow cooler air in. This summer although hot (upper 80s and 90s past few weeks) the humidity has been relatively low - 40% - 55% on average. Interior has been averaging between 74 and 78 degrees and the humidity has stayed pretty steady between 40% - 45%. Was thinking it obviously would help to open the windows at night and in the morning when the temperature drops to low 70s but getting some interesting readings. At night when the temperature drops the humidity goes up - i guess that should not be a huge surprise to me - I guess the amont of moisture in the air stays the same so 37% at 94 degrees turns into 70% at 76 degrees (my readings today). If I open my windows now, would I not be increasing the latent load in my home? Is having a lower temperature the only factor to consider?
Thanks.

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Jul 7, 2010 9:22 AM ET

Free AC by Doug McEvers

I would say open the windows anytime the outside temperature is less than inside. You may be increasing the humidity level inside but you are also cooling the thermal mass inside the building. Adequate attic insulation is one of the keys to minimizing AC usage, if the ceiling is radiating heat so goes the comfort level.

About the Authors

Alex Wilson is founder and executive editor of BuildingGreen, LLC in Brattleboro, VT. He is coauthor of the Consumer Guide to Home Energy Savings (9th edition, 2007) and author of Your Green Home (2006). Content from this blog originally appeared in the Brattleboro Reformer and is more relevant to colder climates. An abbreviated index of this blog can be found here.